1. Field of the Invention
The present invention generally relates to a spectrometer and, more particularly, to a multi-channel imaging spectrometer for eliminating primary aberrations in a conventional linear imaging spectrometer using the design of a lens module to improve the spectrum resolution and reduce the image distortion.
2. Description of the Prior Art
The conventional single-point spectrometer exhibits higher spectrum resolution but is not suitable for fast spectrum measuring on large-area samples because it takes plenty of time to perform two-dimensional shifting if two-dimensional spectrum information is required. An imaging spectrometer with a multi-channel field of view only requires one-dimensional linear shifting to complete two-dimensional spectrum measuring.
U.S. Pat. No. 5,297,555 discloses a multi-channel spectrometer with a linear field of view, using a single-slit as an object so that a light beam passes a collimating lens, a dispersion element (such as a grating or a prism) and a focusing lens to form an image on a planar detector.
Please refer to FIG. 1, which shows chromatic dispersion of a conventional lens module according to the prior art. The curve line 90 indicates the dispersion distribution for the conventional lens module, wherein the focus points for different wavelengths locate on a curve surface towards the axis. When the non-linear dispersion distribution is transformed by a planar detector (indicated by a dotted line 91) to form an image, the sizes of all the focus points for different wavelengths are non-identical to affect the spectrum resolution.
Taiwan Pat. Pub. No. I245114 discloses a spectrometer using a non-spherical lens as a collimating lens and an achromatic lens as a focusing lens. Moreover, U.S. Pat. No. 6,552,788 discloses a multi-channel spectrometer using linear dispersion distribution by the imaging lens so as to overcome conventional problems such as wedge or keystone shape arrangement of color imaging points.
Therefore, there is need in providing a multi-channel imaging spectrometer for eliminating primary aberrations to improve the spectrum resolution and reduce the image distortion.